Field of the Invention
The present invention relates to a positioning apparatus that positions a moving body by using a plurality of position measurement devices being switched with one another, and to a lithography apparatus or an article manufacturing method using such a positioning apparatus.
Description of the Related Art
A lithography apparatus for manufacturing semiconductor devices, liquid crystal devices, or the like includes a positioning apparatus that positions a stage on which a substrate or an original are mounted.
Japanese Patent Laid-Open No. 2002-319541 describes the use of an interferometer as a position measurement device for measuring the position in a Z-axis direction (a direction along the optical axis of an optical projecting system) of a stage. Measurement light from the interferometer that progresses along the Z-axis direction is reflected at a mirror located on an upper surface of the stage. The interferometer measures the position on the basis of an interference pattern generated by interference between the reflected light and reference light.
In addition, Japanese Patent Laid-Open No. 2002-319541 describes the use of a plurality of interferometers and a plurality of mirrors that are switched with one another in accordance with the position in an XY direction of the stage. As described above, by using the plurality of interferometers and the plurality of mirrors which are switched with one another, even in the case where measurement light from one interferometer is blocked by the optical projecting system, the position of the stage can still be measured by using measurement light from another interferometer.
The position in the Z-axis direction of the stage, detected by the interferometer(s), is used in position feedback control of the stage. However, Japanese Patent Laid-Open No. 2002-319541 describes no details about feedback control of the position in the Z-axis direction.